The present invention relates to a Stirling cycle engine provided with a regenerator that offers improved heat exchange efficiency.
A conventional Stirling cycle engine is provided with, for example, a regenerator as shown in FIG. 6, which is composed of a cylindrical bobbin 3 around the outer surface of which is wound a resin film 2 having very fine irregularities 11 formed on the surface thereof so that gaps are left between different layers of the resin film 2. These gaps result from the resin film 2 having the fine irregularities 11 between different layers thereof. FIG. 7 is a side sectional view of an example of a free-piston-type Stirling cycle refrigerator provided with such a regenerator 1. First, the structure and operation of this free-piston-type Stirling cycle refrigerator 14 will be described.
As shown in FIG. 7, the free-piston-type Stirling cycle refrigerator 14 is provided with an enclosure 6 having working gas such as helium sealed therein, a displacer 17 and a piston 18 that divide the space inside the enclosure 6 into an expansion space 20 and a compression space 19, a linear motor 21 for driving the piston 18 to reciprocate, a heat absorber 12 provided by the side of the expansion space 20 so as to absorb heat from outside, and a heat rejector 13 provided by the side of the compressed space 19 so as to reject heat to outside.
In FIG. 7, reference numerals 22 and 23 represent flat springs that support the displacer 17 and the piston 18, respectively, to permit them to reciprocate under their resilience. Reference numeral 15 represents a heat-rejecting heat exchanger, and reference numeral 16 represents a heat-absorbing heat rejector. These serve to prompt the exchange of heat between the inside and outside of the free-piston-type Stirling cycle refrigerator 14. Between the heat-rejecting heat exchanger 15 and the heat-absorbing heat rejector 16 is provided the regenerator.
In this structure, when the linear motor 21 is driven, the piston 18 moved upward inside the enclosure 6, and compresses the working gas in the compression space 19. Here, the working gas becomes warmer as it is compressed, but simultaneously it is cooled by exchanging heat with the outside air through the heat-rejecting heat exchanger 15. Thus, the process that takes place here is isothermal compression.
Then, the displacer 17, which is so controlled as to reciprocate with a predetermined phase difference kept relative to the piston 18, starts moving downward, and thus the working gas in the compression space 19 is passed through the regenerator 1 to the expansion space 20. Meanwhile, the heat of the working gas is accumulated in the resin film 2 forming the regenerator 1, and thus the working gas becomes cooler.
Next, the piston 18 moves downward, and expands the working gas in the expansion space 20. Here, the working gas becomes cooler, but simultaneously it is heated by absorbing heat from the outside air through the heat absorber 12. Thus, the process that takes place here is isothermal expansion.
Then, the displacer 17 starts moving upward, and thus the working gas in the expansion space 20 is passed through the regenerator I back to the compression space 19. Meanwhile, the working gas receives the heat accumulated in the regenerator 1, and thus becomes warmer. This sequence of events, which together constitute the reversed Stirling cycle, is repeated by the reciprocating movement of the driver, and as a result the heat absorber 12 continues absorbing heat from the outside air and thereby gradually makes it cooler and cooler.
As described above, in the Stirling cycle refrigerator that permits cold to be extracted at the heat rejector 12 by making the working gas reciprocate between the compression space 19 and the expansion space 20 through the regenerator 1, the regenerator 1 accumulates the heat of the compressed, warm working gas and then returns the accumulated heat to the expanded, cool working gas in such a way as to collect cold. Therefore, the larger the amount of heat accumulated in the regenerator, the more efficiently heat can be used, and thus the higher the performance of the Stirling cycle refrigerator can be made.
However, with the regenerator 1 structured as described above, when the resin film 2 wound around the outer surface of the cylindrical bobbin 3 is fitted into the free-piston-type Stirling cycle refrigerator 14, the outer surface of the resin film 2 is not fixed on the inner surface of the enclosure 6. Thus, the working gas tends to leak between the outer surface of the resin film 2 and the inner surface of the enclosure 6. The working gas that so leaks flows between the compression space and the expansion space without contributing to the heat exchange taking place in the regenerator 1. This causes a large loss of heat, and thus lowers the performance of the Stirling cycle engine.
An object of the present invention is to provide a Stirling cycle engine that operates with a reduced loss of heat due to gas leakage by the use of a regenerator so structured as to easy and inexpensive to manufacture and thus with increased heat exchange efficiency in the regenerator.
To achieve the above object, according to the present invention, in a Stirling cycle engine provided with a regenerator arranged between a compression space and an expansion space so as to serve as a flow passage for working gas reciprocated between the compression and expansion spaces and operate by collecting heat from or releasing heat to the working gas, the regenerator is provided with a bobbin, a resin film wound around the outer surface of the bobbin so as to be kept in intimate contact therewith, and a sheath fitted around the outer surface of the resin film and having a slit formed in a longitudinal direction. Here, one end of the resin film is firmly fitted to the outer surface of the bobbin, the outer surface of the resin film is kept in intimate contact with the sheath, and the working gas flows between different layers of the resin film.
In this structure, no gap is left between the resin film and the sheath nor between the resin film and the bobbin, and thus the working gas does not leak. This helps improve the heat exchange efficiency in the regenerator.
Alternatively, according to the present invention, in a Stirling cycle engine provided with a regenerator arranged between a compression space and an expansion space so as to serve as a flow passage for working gas reciprocated between the compression and expansion spaces and operate by collecting heat from or releasing heat to the working gas, the regenerator is provided with a bobbin, a resin film wound around the outer surface of the bobbin, and a sheath fitted around the outer surface of the resin film and having a slit formed vertically therein. Here, the resin film has one end fixed on the outer surface of the bobbin, and has the other end led out through the slit and fixed to an end surface of the slit or to the outer surface of the sheath. Moreover, the working gas flows between different layers of the resin film.
In this structure, it is possible to minimize the gaps between the resin film and the sheath and between the resin film and the bobbin. This helps improve the heat exchange efficiency in the regenerator.
Alternatively, according to the present invention, in a Stirling cycle engine provided with a regenerator arranged inside an enclosure provided between a compression space and an expansion space so as to serve as a flow passage for working gas reciprocated between the compression and expansion spaces and operate by collecting heat from or releasing heat to the working gas, the regenerator is provided with a bobbin, a resin film wound around the outer surface of the bobbin, and a sheath fitted around the outer surface of the resin film and having a slit formed vertically therein. Here, the resin film has one end fixed on the outer surface of the bobbin, and has the other end led out through the slit and fixed to an end surface of the slit or to the outer surface of the sheath. Moreover, the sheath is press-fitted on the inner surface of the enclosure, and the working gas flows between different layers of the resin film.
In this structure, it is possible to minimize the gaps between the regenerator and the enclosure and thereby prevent the leakage of the working gas out of the regenerator.
In the Stirling cycle engine described above, O rings may be fitted on the outer surface of the regenerator so that no gap is left between the regenerator and the enclosure. This helps prevent the leakage of the working gas between the regenerator and the enclosure. Moreover, a layer of air is formed between the regenerator and the enclosure. This layer of air shields the heat of the working gas so that it does not dissipate by conducting through the sheath to the enclosure, and thus helps improve the heat exchange efficiency in the regenerator.
In the Stirling cycle engine described above, the space between the regenerator and the enclosure may be filled with adhesive so that no gap is left between the sheath and the enclosure. This helps prevent the leakage of the working gas between the regenerator and the enclosure. Moreover, a layer of resin of the adhesive is formed between the regenerator and the enclosure. This layer of resin shields the heat of the working gas so that it does not dissipate by conducting through the sheath to the enclosure, and thus helps improve the heat exchange efficiency in the regenerator.
In the Stirling cycle engines described above, the sheath may have protruding claw portions formed at one end or both ends thereof, with the claw portions folded back onto the resin film so that the resin film is fixed so as not to move vertically. This helps reduce ineffective work by the flow of the working gas and thereby improve the heat exchange efficiency.
In the Stirling cycle engines described above, the sheath may be formed of a highly heat insulating material. This shields the heat of the working gas flowing through the regenerator so that it does not conduct to the enclosure, and thus helps realize a Stirling cycle engine that operates with improved heat exchange efficiency in its regenerator.
In these Stirling cycle engines according to the present invention, the regenerator has a simple structure with a resin film wound between a bobbin and a sheath. This helps realize a Stirling cycle engine that is easy and inexpensive to manufacture.